As information- and communication-based technologies have developed, encryption and decryption have become important ways to protect confidentiality of information. Random numbers are used in many applications including the generation of secret keys for security systems. Accordingly, systems in which security is important frequently use random number generators. Random number generators necessarily generate unpredictable random numbers.
In systems in which security is important, random numbers are not permitted to have periodicity or be regular. In more detail, security systems need to generate perfect random numbers that are unpredictable and have no periodicity. True random numbers (TRNs) generated from physical noise sources are unpredictable and have no periodicity.
In order to generate TRNs, conventional random number generators have used thermal noise or shot noise as a noise source. Alternatively, conventional random number generators have generated clock signals having irregular periods using ring oscillators. However, conventional random number generators have performance degraded due to mismatches based on various reasons.